1. Field of the Invention
The invention relates to a laser welding process using a nozzle designed, adapted and formed so as to be used in laser beam welding, more simply called a “laser nozzle”, which has a particular form enabling the hydrodynamics of the liquid metal pool to be better controlled when said nozzle is employed in a laser beam welding process, through which on the one hand a laser beam and on the other hand a gas pass.
2. Related Art
Laser beam welding is a well known process that is widely used industrially for assembling various materials, such as carbon steel, stainless steels, aluminum and light alloys etc.
Schematically, in order to implement a laser welding process, a laser source or generator is used for generating a laser beam that is conveyed via an optical fiber or via other optical means such as mirrors, lenses, etc. to one or more parts to be welded. The energy of the beam makes it possible to melt the constituent parts and in this way to obtain, after cooling, a weld bead between the parts to be welded.
In order to prevent contamination of the weld bead by atmospheric impurities, a shielding gas is normally used for protecting the welding zone. The type of shielding gas chosen depends in particular on the nature of the material constituting the parts to be welded, but gases such as helium, argon, nitrogen, CO2, oxygen, hydrogen (to a certain extent) and mixtures thereof are conventionally used.
In order to deliver the shielding gas and the laser beam, a nozzle commonly called a “laser nozzle” is normally used.
Laser nozzles used on laser welding machines conventionally have a cylindrical, conical or tapered shape and are drilled in their center with a central passage through which the laser beam passes and into which the shielding gas is introduced so as to be distributed above the welding zone coaxially to the laser beam.
This type of nozzle enables the shielding gas to be distributed in the vicinity of the zone of interaction between the laser beam and the material to be welded and to inert it. Inerting this zone makes coupling between the laser beam and the material effective, while protecting the molten metal pool from atmospheric contamination.
However, gas flows are usually laminar and slow. In point of fact, the gas jet distributed by this type of nozzle does not exert a dynamic force on the molten metal pool and does not affect the hydrodynamic flows of the molten metal pool forming during welding.
These types of slow flow lead to satisfactory welding results under standard conditions of use. However, with these types of flow, many welding configurations exist where laser welding is impossible, for example welding of stacks of several metal sheets coated with zinc or the like with zero play between them.